Care guide · Freshwater snails

Black Faunus snail

Faunus ater

Faunus ater. Photo: -serwacy01-, CC BY-SA 4.0; resized and compressed. Photo: -serwacy01- (Wikimedia Commons) · Source · CC BY-SA 4.0Resized and compressed; no cropping or colour changes.

Faunus ater is a large snail from the Indo-West Pacific, recognised by its smooth, dark, high-spired shell. It is chiefly associated with estuaries and lower river reaches influenced by brackish water, but it has also been recorded in freshwater habitats. Aquarium sources recommend mineral-rich water and a spacious, mature tank; the species is also kept in freshwater. That does not make freshwater housing equivalent to its natural habitat. Choose a water type deliberately, never change salinity abruptly, and buy only when the species identification is reasonably checked.

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At a glance

Temperature: 22–28 °C
pH: 7.0–8.0
Diet: Omnivore
Adult size: Up to 9 cm
Group size: At least 2 individuals
Temperament: Peaceful

About this species

GBIF accepts Faunus ater (Linnaeus, 1758). The sources used here place it in Pachychilidae, although older literature used several family placements. B-Aqua lists Faunus melanopsis, Melanopsis princeps, Pirena terebralis, Strombus ater and Turritella fuscata among synonyms. Trade names include Black Faunus and Black Devil snail. “Cappuccino snail” is an inconsistent trade or colour-form label and is not treated here as a confirmed synonym. Its tall dark shell can resemble those of other snails, so a shop label alone is not a reliable identification.

Natural habitat

The species occurs across the Indo-West Pacific. Researchers documented Faunus ater in Singapore in an artificial pond and a drain leading to the sea; the pond was brackish and conditions in the drain varied widely. Their paper also cites older records from freshwater and slightly brackish rivers, estuaries and lagoons, and stresses that ecology and reproduction are incompletely known. These field observations describe particular sites, not aquarium targets. B-Aqua characterises the species chiefly as estuarine and recommends an estuary biotope. Never release aquarium animals, plants or water into natural waters.

Aquarium and layout

Set up a spacious, fully mature aquarium with a soft sandy or muddy substrate that the snail can burrow through. B-Aqua gives 50 litres as a minimum and 100 litres as a recommendation for several animals; this is husbandry guidance, not an experimentally established biological threshold. The snail may reach about 9 cm and spends much of its time buried. Allow ample floor area, stable cover and surfaces where food and biofilm can develop. Decide in advance whether the system is freshwater or brackish; do not imitate an estuary by adding an arbitrary amount of salt. Measure salinity reliably and avoid rapid changes.

Water conditions

The B-Aqua profile graphic indicates approximately 22–28 °C and pH 7–8 as care guidance. The same source recommends mineral-rich/harder water and warns against rapid salinity changes. The Singapore field study recorded specific gravity 1.002–1.008 at one pond and 1.002–1.025 in a drain. Conditions varied greatly at those sites, so the figures are not general aquarium settings. We therefore do not publish a precise salinity, GH or KH target. The species is chiefly associated with brackish water, but freshwater records and freshwater aquarium keeping also exist. These situations should not be presented as identical.

Behaviour and group size

B-Aqua describes Faunus ater as peaceful, gregarious, nocturnal and burrowing. It forages mainly on the bottom and may spend long periods under the substrate; that alone does not indicate illness. Protect it from animals that nip its tentacles or crush its shell; the profile warns about crayfish and crabs. A suitable tankmate must also tolerate the same water type, salinity and temperature regime. Do not judge compatibility from temperature overlap alone. The linked neon tetra is marked unsuitable for a brackish setup because the water environments differ, not because aggression has been demonstrated.

Feeding

This is an opportunistic omnivore that B-Aqua says feeds mainly on biofilm and algae, as well as scavenged material and food remains. A mature substrate, leaf litter and natural grazing surfaces matter; do not expect one snail to clean aquarium glass. B-Aqua also mentions vegetables and leftovers, but this is not a controlled species-specific feeding trial. The manually verified catalogue offers are formulated for fish. No product is selected without checked ingredients and explicit support for safe snail feeding. Feed modestly, remove leftovers and monitor shell condition. A damaged shell calls first for a review of water chemistry and husbandry.

Breeding

Lok et al. describe reproductive biology as largely unknown. They identify the species as egg-laying and say a long free-swimming larval phase has been suggested because of its wide distribution. B-Aqua calls Faunus ater amphidromous and states that reproduction involves brackish water and larval development in seawater. Since the scientific field paper stresses uncertainty, we present that latter account as the specialist aquarium profile’s view, not as a fully established captive-breeding protocol. Do not expect easy propagation in a standard freshwater tank or promise captive-bred stock. Ask about provenance and never release animals into outdoor waters.

Keeping with fish

Neon tetra (Paracheirodon innesi): unsuitable in a brackish estuary setup. The fish’s usual care is freshwater-oriented and does not fit a brackish regime selected for Faunus ater. This is an assessment of water environment, not evidence of aggression or direct harm between the two species. Keeping them in freshwater would be a different husbandry choice, but it does not automatically establish optimal conditions for the snail. No controlled pairing trial was found.

Keeping with other invertebrates

Java fern (Microsorum pteropus): conditional in mildly brackish water. Aquarium-care references describe tolerance of mildly brackish conditions. Attach its rhizome to wood or rock; Faunus ater burrows and may dislodge weakly rooted plants. Do not assume tolerance at higher salinities. Acclimate the plant gradually to the chosen environment and monitor growth. This is a cautious setup pairing based on general species husbandry; no direct Faunus ater trial was found.

Exoskeleton, shell and minerals

Snails do not moult like shrimp. Their shell grows, and visible erosion or pits can be associated with water chemistry or damage. B-Aqua warns that low pH and low calcium may affect shell condition; Lok et al. describe a thick dark outer layer that protects the shell in acidic habitat, but erosion may follow if it is abraded. Do not add minerals or salt blindly. First check temperature, pH, hardness and the stable salinity chosen for the biotope. Abrupt transitions between fresh and brackish water are specifically discouraged.

Possible problems

Key risks include misidentification, an undersized or immature tank, too little food at the bottom, insufficient minerals, shell damage, rapidly changing salinity and unsuitable tankmates. Burrowing may uproot rooted plants. Choose a consistent freshwater or brackish plan before purchase and maintain it steadily; field salinity is not a ready-made aquarium recipe. If the snail remains retracted, inactive for a prolonged period or develops shell erosion, first check water measurements and housing. Never release animals or aquarium water into streams, ponds or coastal water.

Sources & review

This care guide draws on several specialist sources and was last checked on 18 October 2026.

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